The invention relates to an apparatus and a process for recording photometric data that is positioned side by side or in succession on a page-like or strip-like print.
Apparatuses for recording photometric data, so-called densitometers, are variously employed in the photographic industry and in graphics, particularly in printing shops. Basically, densitometers can be employed in all areas that work with preset printings or with test printings. In addition to the mentioned areas of application, densitometers can play a role in desk-top publishing.
In the photographic industry, densitometers are used both in the routine control of apparatus parts involving wet chemistry and in inspecting the adjustment of the photographic copier or photographic printer. In inspecting apparatus parts involving wet chemistry, i.e., the developing baths for film or paper, corresponding chemical strips of film or paper are subjected to measurement. These strips have already been exposed in a standardized fashion by the film or paper manufacturer and are developed over regular distances in the given film or paper developing baths. The developed film or paper strips are photometrically evaluated with the densitometers and are compared with the manufacturer's theoretical specifications. Depending on the results thus ascertained, the developing baths are freshened or supplemented, renewed, or left unchanged. To inspect the adjustment of the photographic printer, one or several standard negatives are exposed on photographic paper and are developed with a tested chemical process. The developed images are photometrically evaluated with the densitometer and compared with the theoretical values. The basic setting of the photographic printer may be modified according to the values ascertained.
This general type of apparatus for recording photometric data on film or paper strips is described in U.S. Pat. No. 5,118,183. The densitometer apparatus is equipped both for reflectance operation with opaque test strips and for transmission operation with transparent test strips and accordingly exhibits a stationary reflectance measuring lens and a stationary transmission measuring lens. Stationary filters in the apparatus also permit the reflectance and transmission densities of the test strip to be determined for different wavelengths, chiefly for the three primary colors of red, green, and blue. A motorized transport device incorporated in the apparatus moves the test strip along the apparatus. A lateral guide element permits improved positioning of the test strip, which is fed into the apparatus through an intake slot. The lateral guide unit can be manually adjusted to the specific width of the test strip. To also permit the evaluation of test strips that have more than one column of test fields--which, for example, can be brought side by side on the test strip in the longitudinal direction--not only can the lateral guide unit be adjusted in its width, it can also be moved in its entirety in a direction transverse to the intake direction of the test strip into the apparatus. This makes it possible to measure several adjacently positioned columns of measuring fields, given some skill and patience.
The film and paper test strips of different manufacturers generally exhibit differently positioned measuring fields. The measuring fields differ in size and, particularly in the case of paper strips, may be positioned side by side in one or several columns. The positioning of successive measuring fields relative to a central track of a column may differ, that is, individual measuring fields may be slightly displaced relative to this central track. Neighboring measuring field columns may also exhibit a different number of measuring fields. The first measuring field of a column may not necessarily be positioned at the same distance from the front edge of the test strip as the first measuring field of the neighboring column. The test strips of different manufacturers thus differ considerably in design. An operator who wishes to measure a test strip with the known apparatus must orient the strip with a great degree of care to assure that the measurement is made at the correct point. Apart from the fact that this orientation process is time-consuming, it is difficult to record measuring fields which may have a displaced position relative to the central track of a column. Here the operator must first visually assess the test strip and then decide which section of the test strip must be fed in displaced fashion relative to the central track of the column, in order to measure both centrally positioned and displaced measuring fields. This is frequently difficult to master, and an erroneous feed of the test strip may result in incorrect measurements and the need to repeat the process. With certain test strips it may even be the case that lateral displacement is insufficient to reach all the measuring fields of a column.
In a known apparatus, a test strip is automatically transported through the apparatus. A pair of rollers, one of which is driven, seizes the advancing end of the test strip and pulls it through. Once the test strip has been seized by the roller pair, it can no longer be displaced laterally. If the test strip exhibits more than one column of measuring fields for measurement, it is consequently necessary to completely measure one column first, and the test strip must transported completely through the apparatus. The test strip is then fed into the apparatus in a laterally displaced position, in such a way that the measuring fields of the adjacent column can be evaluated, etc. Thus, the test strip must be separately oriented for each measuring column, and each time the operator must decide anew which portion of the test strip must be laterally displaced to assure that all measuring fields are reliably covered.